A control system is configured by a programmable logic controller (also referred to as programmable controller) and an extension unit such as a network unit. The programmable logic controller and the extension unit are controlled by a sequence program.
The sequence program is created by an engineering tool, which is a sequence-program-creation supporting apparatus. When the sequence program causes the programmable logic controller and the extension unit to execute processing, a command specific to an apparatus defined in advance (hereinafter referred to as dedicated command) is described in the sequence program.
The dedicated command is configured by a command name and control data. The control data is stored in a device in the programmable logic controller. The programmable logic controller and the extension unit execute the processing on the basis of setting values stored in the device.
Patent Literature 1 discloses a program-creation supporting apparatus that acquires system configuration information of an extension unit connected to a CPU unit (Central Processing Section module), sets, on the basis of information concerning a type of the extension unit, as a search target, a command word for instructing operation of a controlled apparatus connected to the extension unit, and extracts and displays a command word corresponding to a character string of an input command. Patent Literature 2 discloses a programming apparatus for a programmable controller with which an operator performs input operation according to guidance to create a sequence program. Patent Literature 3 discloses a control-program creating apparatus with which an operator inputs, on an editing screen of a control program displayed in a ladder format, to add device designation, an input box of a command or a memory address for designating a device and an input box of a device comment to display a ladder diagram with the device comment. Patent Literature 4 discloses a control-system engineering apparatus that reads out system configuration information and a status from project information of a PLC (Programmable Logic Controller) and comprehends a network to be connected.